As far as safety goes, the only thing that matters is safety certification from independent authorities. As of today that means CE EN1078 and CPSC. MIPS certification is not independent, and the testing performed is determined by MIPS themselves, and as far as I can tell, there is zero independent evidence that it provides measurable safety benefit.

Other than that, the only other factors that come in to play with a helmet are fit (the most important in my opinion), weight, ventilation, and style.

Pick a helmet that is certified, that feels good on your head, and that you think looks cool. Beyond that, whatever makes you feel good about spending all that money.